Field of the Invention
Embodiments of the invention generally relate to a cementing operation. More particularly, embodiments of the invention relate to a valve assembly for use during a cementing operation.
Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thus formed between the string of casing and the wellbore. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing strengthens the wellbore, and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.
During a cementing operation, a float shoe is attached to the bottom of the casing string, which is run into the wellbore. The float shoe typically has a one-way valve located within the shoe. The casing is run into the wellbore to the desired depth and a cementing operation is performed. The cementing operation commences with a first plug being dropped into the casing. The first plug typically has a through bore with a rupture disk therein. Behind the plug, cement is pumped into the casing. Following the cement, a second typically solid plug is dropped into the casing. The first plug lands on the float shoe. As the pressure of the cement behind the first plug increases, the rupture disk fails. The cement flows through the bore of the first plug and past the one-way valve in the float shoe until the second plug reaches the first plug. The one-way valve allows the cement to flow out of the float shoe and into the annulus between the casing and a wellbore therearound, while preventing the cement from re-entering the casing string. Typically, the one-way valve in the float shoe includes a flapper valve or a poppet valve. However, these valves are not designed to hold wellbore pressure. Therefore, there is a need for a valve that can hold wellbore pressure.